Abstract: The purpose of this lab is to determine whether a homemade soap, a bar soap or liquid soap kills bacteria better. The homemade soap was created by dissolving sodium hydroxide, lye, in water and mixing it with melted lard and cooling it overnight. After the homemade soap was created, a certain amount of soap was dissolved in water and paper test circles were soaked in the mixtures. The test circles were then placed on bacterial agar plates and placed in an incubator overnight. The next day the zone of inhibitions were measured, and the liquid soap produced a .25 cm ring, the bar produced a .05 cm ring, the homemade soup produced a .02 cm ring, and the control soaked in only water, did not produce a ring at all. It was predicted that the liquid and the bar soap would produce the greatest zone of inhibitions, and it proved correct by the data, although the liquid produced the greatest zone of inhibition out of all of the soaps tested. A possible reason the homemade soap did not produce a large ring could be because there was too much lard in the mixture when the soap was created and was therefore unable to dissolve in the water. In the second trial, a smaller amount of lard was used. The second recipe used 20 g less lard, but the results still showed there was too much lard. A possible reason the bar soap did not produce as great of a ring as the liquid soap could be not all of the soap dissolved in the water, making the mixture not as strong. Soap is used to kill bacteria, preventing the growth of bacteria and to clean household surfaces and human surfaces.
Key Words: Soap, Zone of Inhibition, Bacteria, Bacterial Growth
A smaller amount of lard will allow the soap to dissolve in water.
Article: Blank, I. (1939). Action of soap on skin. Retrieved from http://archderm.ama-assn.org/cgi/content/summary/39/5/811
Second Procedure:
How to make the homemade soap: http://www.millersoap.com/pennwaltetc.html#Preparing%20Fat
agar:water, nutrient agar
Soap: Fat, Water, Lye, Box, clean cotton fabric
Bacterial Solution
Store bought Soaps
Information on the zone of inhibition: http://www.antimicrobialtestlaboratories.com/Zone_of_Inhibition_Test_for_Antimicrobial_Activity.htm
Link to Bar Soap vs. Liquid Soap:http://health.howstuffworks.com/skin-care/cleansing/products/bar-soap-liquid-soap.htm
Link to Pros and Cons of Bar Soap:http://health.howstuffworks.com/skin-care/cleansing/products/bar-soap-liquid-soap1.htm
Link to Pros and Cons of Liquid Soap:http://health.howstuffworks.com/skin-care/cleansing/products/bar-soap-liquid-soap2.htm
Link to Anti-Bacterial vs. Non Anti-Bacterial Soap:http://health.howstuffworks.com/skin-care/cleansing/myths/question692.htm
Link to What Makes Soap Anti-Bacterial:http://illumin.usc.edu/68/what-makes-antibacterial-soap-antibacterial/
The purpose of this lab is to determine whether a homemade soap, a bar soap or liquid soap kills bacteria better. The homemade soap was created by dissolving sodium hydroxide, lye, in water and mixing it with melted lard and cooling it overnight. After the homemade soap was created, a certain amount of soap was dissolved in water and paper test circles were soaked in the mixtures. The test circles were then placed on bacterial agar plates and placed in an incubator overnight. The next day the zone of inhibitions were measured, and the liquid soap produced a .25 cm ring, the bar produced a .05 cm ring, the homemade soup produced a .02 cm ring, and the control soaked in only water, did not produce a ring at all. It was predicted that the liquid and the bar soap would produce the greatest zone of inhibitions, and it proved correct by the data, although the liquid produced the greatest zone of inhibition out of all of the soaps tested. A possible reason the homemade soap did not produce a large ring could be because there was too much lard in the mixture when the soap was created and was therefore unable to dissolve in the water. In the second trial, a smaller amount of lard was used. The second recipe used 20 g less lard, but the results still showed there was too much lard. A possible reason the bar soap did not produce as great of a ring as the liquid soap could be not all of the soap dissolved in the water, making the mixture not as strong. Soap is used to kill bacteria, preventing the growth of bacteria and to clean household surfaces and human surfaces.
Key Words: Soap, Zone of Inhibition, Bacteria, Bacterial Growth